Spinal implants such as interbody fusion devices are used to treat degenerative disc disease and other damages or defects in the spinal disc between adjacent vertebrae. The disc may be herniated or suffering from a variety of degenerative conditions, such that the anatomical function of the spinal disc is disrupted. Most prevalent surgical treatment for these conditions is to fuse the two vertebrae surrounding the affected disc. In most cases, the entire disc will be removed, except for a portion of the annulus, by way of a discectomy procedure. A spinal fusion device is then introduced into the intradiscal space and suitable bone graft or bone substitute material is placed substantially in and/or adjacent the device in order to promote fusion between two adjacent vertebrae.
There are a variety of implants for spinal fusion in current use, some of which are expandable and others of fixed dimension. In order to accommodate the spinal anatomy and promote arthrodesis, an interbody fusion device preferably has optimized contact with adjacent endplates. This is commonly achieved by ensuring that the interface between the device and the bony endplates of opposing vertebral bodies includes a surface area as large as practicable. In turn, this means that the distal tip of the device is often restricted to have a blunt nose, making it challenging for the surgeon to insert the device in the intradiscal space. A common approach to surmounting this challenge is to form the distal tip of the implant with a bullet-type nose. Such an implant is described, for example, in U.S. Pat. No. 5,766,252 issued to Henry et al. on Jun. 16, 1998. The potential disadvantage to such design is that while the implant is easier to insert and impact into the intradiscal space, it offers less interface area between the implant and the endplates since the bullet nose portion of the device does not contact the endplates. In addition, when such implants are inserted posteriorly, the bullet nose is situated ultimately in the anterior portion of the intradiscal space and disadvantageously occupies space where bone graft is preferably placed to improve arthrodesis.
Accordingly, there is a need to develop an interbody fusion device and insertion technique that provides the advantages of the bullet nose devices while optimizing the contact area between the device and the opposing vertebral endplates.